In accordance with principles of the invention generally relates to a method of mounting devices on a substrate and a device-mounting substrate structure thereof, in which terminal connection of the devices is performed by using a wiring line of the substrate as a seed metal using electrolytic plating.
In order to mount devices such as a semiconductor chip or a separate component in a wiring substrate made of a semiconductor or resin, the device may be mounted in one surface or both surfaces of a single wiring substrate as in a typical print wiring substrate, or may be mounted in a multilayered wiring substrate.
Among them, in order to manufacture a multi-layered wiring substrate, there is known a method (build-up) in which the device is mounted in a conductive layer formed in one surface of the base substrate, and a multi-layered substrate is built up in a single side by repeating formation of the inter-layered insulation layer, formation of the wiring line, and device mounting. In addition, there is also a known method of, for both surfaces of the core substrate, forming the wiring line, forming the inter-layered insulation layer, and performing device mounting.
A method of stacking other bare chips on a semiconductor substrate (base chip) while connection between terminals is obtained is also a type of the build-up method.
In the case where the devices are mounted in the wiring substrate, particularly, in the case where devices to be mounted are minute and plural, a technique of collectively arranging (transferring) a plurality of devices in the wiring substrate with a high precision is important.
Such a device-transferring technique is disclosed, for example, in JP-A-2004-273596. In this disclosure, a device is held in the resin layer on a first substrate, the first substrate is bonded to a second wiring line from the side of the resin layer while the device is held, and exfoliation is performed at the interface between the resin layer and the first substrate, so that the devices are collectively transferred to a second separate substrate.
Such a device transferring method is particularly effective when the substrate area is significantly large. In addition, the method of holding the devices in the resin layer and collectively transferring the devices into a separate substrate is further effective when a significantly large amount of devices are to be regularly arranged with a high precision.
JP-A-2004-273596 discloses a method of manufacturing an LED display in which light is emitted from the LED device for this purpose.
However, it is desirable to provide robust bonding between the electrode pad of the device and the wiring line both mechanically and electrically after arranging the devices in the wiring substrate regardless of whether the devices are mounted in a single-layered substrate or a multi-layered substrate without being limited to a case where such devices are collectively transferred.
In this regard, Japanese Patent No. 3956955 and JP-A-2005-311109 disclose an electroless plating method as a method of connecting the devices and the wiring substrate.
JP-A-2004-273596 discloses a method of connecting terminals between the wiring substrate and the mounted devices using electroless plating in examples thereof.
In addition, according to JP-A-2005-311109, a material called an under-fill is coated on the wiring substrate using a micro-dispenser or the like, and devices (semiconductor laser) are bonded thereon. The devices are arranged using an apparatus capable of obtaining alignment such as a flip-chip bonder. In this case, a gap between the device pad and the wiring line is formed to be several to ten micrometers μm, and the electroless plating process is performed in this state.